Peppermint oil is used to address gastrointestinal problems because it inhibits the smooth muscles in the gastrointestinal tract from contracting. Unfortunately, however, if peppermint oil is released in the stomach, it is absorbed quickly and can upset the stomach. To overcome this problem, others have developed enteric coated peppermint oil formulations that allow the peppermint oil to pass into the intestines before it is released.
In conventional enteric coated peppermint oil formulations, the peppermint oil is loaded into a hollow capsule that is enteric coated. The enteric coating prevents the capsule from dissolving in the stomach, but allows the capsule to dissolve in the intestines and release the peppermint oil.
Single-unit enteric coated peppermint oil capsules such as these have several drawbacks. First, the dose of peppermint oil that is actually absorbed by the intestines of the person taking the capsule is unpredictable. One of the reasons for this is that, when the capsule dissolves, it quickly dumps all of the peppermint oil into the same area of the intestines, which is problematic because peppermint oil is not very water soluble. Another of the reasons for this is that food in the gastrointestinal tract affects the amount of peppermint oil absorbed.
A second drawback associated with single-unit enteric coated peppermint oil capsules is that the onset of action of the peppermint oil is unreliable. The primary factor delaying the onset of action is the amount of time the capsule spends in the stomach, which ranges over several hours and depends on the amount of food in the stomach. In order to get a reliable onset of action, one should take the capsules on an empty stomach. But because some gastrointestinal disorders flare up after a meal, people often want to treat the flare up immediately. Accordingly, the single-unit enteric coated capsules are not ideal for treating acute gastrointestinal flare ups that are triggered by food.
A third drawback associated with single-unit enteric coated peppermint oil capsules is the fact that peppermint oil is volatile. If the capsules are shipped or stored much above room temperature for extended periods of time, the peppermint oil can evaporate and permeate the capsule.
We surmised that these problems could be addressed by developing enteric coated multiparticulate compositions containing peppermint oil, but found that it is difficult to do so because peppermint oil is very volatile. If multiparticulate cores containing peppermint oil are heated or stored for extended periods, much above room temperature, the volatile components of the peppermint oil leave the cores and permeate the enteric coating. This made it difficult to process the cores, especially when it came time to cure the enteric coating on the cores at elevated temperatures.
In U.S. patent publication 2012/0207842, we described making enteric coated multiparticulate L-menthol compositions. In order to prevent the L-menthol from sublimating as the cores were being processed, we resorted to low temperature processing techniques. The L-menthol multiparticulate compositions described in that application provided the release profile that we desired and worked well for some applications, but were not optimized for all applications.
We have identified a need for a peppermint oil composition that avoids the drawbacks associated with single-unit enteric coated capsules and can be made using conventional room temperature processing techniques